As player he won the championship of the German Democratic Republic of 1952 with Turbine Halle, today known as Hallescher FC.
Major successes were the promotions to the Bundesliga attained with Eintracht Braunschweig and Borussia Dortmund, albeit with the latter he was dismissed before the end of the season.
While Knefler refused, some of his teammates, such as Lothar Ulsaß, Horst Wolter, and Wolfgang Grzyb, accepted bribes and were later punished in the wake of the so-called Bundesliga scandal.
Knefler thereafter was replaced with Branko Zebec and moved on to then second division club Borussia Dortmund finishing the season sixth.
With a team of unfancied players he reached the semifinal of the German Cup in 1975, there only losing 1–2 away after extra time to MSV Duisburg - which lost the final 0–1 to Eintracht Frankfurt, coached by Knefler's former assistant Dietrich Weise.
His time at the club which was relegated in 1972, was marred by internal jealousies, that presumably were a major factor behind his premature demise in the end of January 1976.
With the Austrian playmaker Kurt Jara and the attackers Rudi Seliger and Ronald Worm and the solid defence around Bernard Dietz and Detlef Pirsig the club finished ninth.
Knefler retired for medical reasons - half of his stomach had to be removed[3] - but returned from matchday 10 for six matches to the coaching bench in Duisburg.
On the return from a Cup-match in Bremen on 23 September 1978 - where the Eintracht with players like Jürgen Grabowski, Bernd Hölzenbein and the Austrian Bruno Pezzey won 3–2 - Knefler sustained severe injuries in a car accident so that he had to abandon his career in December, after 16 league matches, the Eintracht then being sixth in the league.